Muscle ubiquinone in male effort angina patients

Seven (7) males with effort angina and listed for coronary by-pass surgery had muscle biopsies taken from their vastus lateralis muscle for determination of muscle fiber types (%ST), ubiquinone (vitamin Q, UQ), oxidative and fermentative enzyme activities. Graded cycle ergometer exercise to determine intensities corresponding to onset of blood lactate accumulation set to 2.0 nimol × 1^–1 (W_OSLA) and symptom limited exercise (maximal, W_SL) were also undertaken. W_OBLA was positively related to %ST (r = 0.92, p < 0.001). %ST was on the other hand inversely related to UQ (r =–0.82, p < 0.05), the heart specific LD subunit LD-H (r =–0.96, p < 0.001), the isozyme LD₃ as the fraction of LD (%LD3) (r=–0.93, p < 0.01), and the CK isozyme CKMB as the fraction of CK (%CKMB) (r = –0.88, p < 0.05). It was suggested that muscle UQ depletion in the patients was related to molecular oxygen and free oxygen radical formation. The lack of antioxidants then caused a radical trauma specifically to the ST fiber and their mitochondria. This could be a cause and-effect explanation for the selective ST fiber downregulation in effort angina and heart failure in general.     

Muscle fibers,ubiquinone and exercise capacity in effort angina

Seventeen male patients with ischaemic heart disease (IHD) and effort angina performed OBLA exercise stress tests (set to 2.0 mmol × 1^–1). They had muscle biopsies from the vastus lateralis muscle the day before coronary by-pass grafting, and from the internal and external intercostal, diaphragm and gastrocnemius muscles during surgery. They had a low W_OBLA (83 ± 6 W, mean ± 1 S.E.M), W_OBLA corresponded to 79 ± 4% (% W_OBLA) of W_SL (symptom limited or maximal capacity = 111 ± 11 W). Peak blood lactate concentration averaged 2.9 mmol × 1^–1. Muscle fibre composition disclosed a depressed percent slow twitch (ST or red) muscle fibres in the vastus lateralis and intercostal muscles (%ST). The diaphragm and gastrocnemius muscles had normal %ST. Intercostal muscles had elevated values for the fast twitch muscle fibre (FT) subgroup FTa indicative of endurance adaptation. The vastus lateralis, gastrocnemius and diaphragm muscles had normal muscle ubiquinone (UQ) contents, whereas the intercostals were depleted. Plasma contents of the antioxidants UQ and -tocopherol were low as compared to healthy man.The study was carried out by the Department of Thoracic Surgery, Karolinska Hospital, Stockholm, Sweden.     

Muscle metabolism and quality (MQI) in prediabetic sedentary man

Twelve pairs of healthy sedentary males matched for their body mass index (BMI) with either a low insulin response (LIR; a stage of prediabetes) or a high (HIR; controls) to a standardized glucose infusion test (GIT) were studied in respect to their exercise capacities (W_OBLA, W_SL and relative W_OBLA: W_OBLA × W_SL-1 × 100), muscle fiber composition (%ST), muscle citrate synthase activity (CS), muscle ubiquinone (MUQ), MUQ over %ST (muscle quality index, MQI), and peripheral insulin sensitivity (PIS) as described with insulin-clamp techniques (SIGITmean). LIR and HIR displayed normal PIS and positive relationships versus exercise capacity. LIR's but not HIR's relative W_OBLA was related to CS as earlier only documented in endurance athletes but at a lower level than both in HIR and athletes. This pointed at a poor peripheral oxygen delivery in LIR. LIR's MQI decreased relative to HIR's the higher the muscle CS indicating radical related muscle trauma in LIR as in athletes. LIR representing prediabetes described muscle anomalies, which could represent prestages of the lesions observed in type-2 diabetes. They are claimed to be responsible for insulin-, glucose-, lipid-resistance, and peripheral circulatory resistance.     

Coenzyme Q10 and key enzyme activities in papillary muscle related to left ventricle function in mitral valve disease

Coenzyme Q₁₀ (CoQ₁₀) was studied in papillary muscle from 18 patients (52–67 years, 2 females) subjected to open heart surgery due to mitral valve disease. In addition the enzyme activities of lactate dehydrogenase (LD) with its five isozymes, citrate synthase (CS) and mitochondrial CK (CK-MIT) were determined. Myocardial function was assessed by means of left ventricle (LV) angiography. CoQ₁₀ averaged 0.39 (range 0.26–0.59) g × mg^–1 dw. On an individual basis CoQ₁₀ was related to CS activity although not as closely as CK-MIT (r = 0.45, p<0.05 versus r = 0.86, p<0.001). The ratio (CoQ₁₀) × (CS activity)^–1 was calculated to represent mitochondrial quality. The level of LD₃ fraction increase was used to mark for the degree of metabolic stress in the heart. LD₃ fraction was negatively related to the quality index (r = –0.71, p<0.001). Thus, those with a low CoQ₁₀ per unit of CS activity had also a high LD₃ isozyme fraction. In a subset of 12 patients with isolated mitral regurgitation due to myxomatous valve degeneration, CoQ₁₀ and the ratio CoQ₁₀ over CS decreased with the degree of LV function impairment (r = –0.58, p<0.05 and r = –0.68, p<0.05, respectively). The quality index takes into account not only enzyme activity but also the potential for control of free oxygen radicals.     

Exercise and recovery metabolism in the pacific spiny dogfish (<Emphasis Type="Italic">Squalus acanthias</Emphasis>)

We examined the effects of exhaustive exercise and post-exercise recovery on white muscle substrate depletion and metabolite distribution between white muscle and blood plasma in the Pacific spiny dogfish, both in vivo and in an electrically stimulated perfused tail-trunk preparation. Measurements of arterial-venous lactate, total ammonia, -hydroxybutyrate, glucose, and l-alanine concentrations in the perfused tail-trunk assessed white muscle metabolite fluxes. Exhaustive exercise was fuelled primarily by creatine phosphate hydrolysis and glycolysis as indicated by 62, 71, and 85% decreases in ATP, creatine phosphate, and glycogen, respectively. White muscle lactate production during exercise caused a sustained increase (~12 h post-exercise) in plasma lactate load and a short-lived increase (~4 h post-exercise) in plasma metabolic acid load during recovery. Exhaustive exercise and recovery did not affect arterial PO₂, PCO₂, or PNH₃ but the metabolic acidosis caused a decrease in arterial HCO₃^– immediately after exercise and during the first 8 h recovery. During recovery, lactate was retained in the white muscle at higher concentrations than in the plasma despite increased lactate efflux from the muscle. Pyruvate dehydrogenase activity was very low in dogfish white muscle at rest and during recovery (0.53±0.15 nmol g wet tissue^–1 min^–1; n=40) indicating that lactate oxidation is not the major fate of lactate during post-exercise recovery. The lack of change in white muscle free-carnitine and variable changes in short-chain fatty acyl-carnitine suggest that dogfish white muscle does not rely on lipid oxidation to fuel exhaustive exercise or recovery. These findings support the notion that extrahepatic tissues cannot utilize fatty acids as an oxidative fuel. Furthermore, our data strongly suggest that ketone body oxidation is important in fuelling recovery metabolism in dogfish white muscle and at least 20% of the ATP required for recovery could be supplied by uptake and oxidation of -hydroxybutyrate from the plasma.Abbreviations CoA-SH free coenzyme A - CPT-1 carnitine palmitoyltransferase-1 - CrP creatine phosphate - H⁺_m metabolic proton load - Lac lactate load - PDH pyruvate dehydrogenase - PVP polyvinylpyrrolidone - SCFA-carnitine short-chain fatty acyl-carnitine - TAG triacylglycerol - TENS trancutaneous electrical nerve stimulator Communicated by: L.C.-H. Wang     

The relationship of creatine kinase variability with body composition and muscle damage markers following eccentric muscle contractions

[Purpose]

The purpose of the study was to investigate the relationship between CK variability and body composition and muscle damage markers following eccentric exercise.

[Methods]

Total 119 healthy male subjects were recruited to perform 50 eccentric contractions consisted of 2 sets of 25 contractions. Then, blood creatine kinase (CK) activity was analyzed to divide into three groups based on their CK activity levels. Maximum isometric strength (MIS), muscle soreness (SOR) and body composition data were obtained before and after exercise.

[Results]

The results showed that high CK responders had a significant decrease in MIS (p<0.001) and greater SOR (p<0.01) following eccentric exercise compared to low CK responders. Percent body fat was also higher in high responders compared to low responders (p=0.014). Peak CK activity was significantly correlated with MIS and SOR but no correlation with % body fat, muscle mass, and body mass index.

[Conclusion]

CK variability following eccentric exercise is closely related to MIS and SOR and % body fat may be a potent factor for CK variability.     

Influence of isolation media on synaptosomal properties: Intracellular pH,pCa, and Ca2+ uptake

Preparations of synaptosomes isolated in sucrose or in Na⁺-rich media were compared with respect to internal pH (pH₁), internal Ca²⁺ concentration ([Ca²⁺]_i), membrane potential and⁴⁵Ca²⁺ uptake due to K⁺ depolarization and Na⁺/Ca²⁺ exchange. We found that synaptosomes isolated in sucrose media have a pH_i of 6.77±0.04 and a [Ca²⁺]_i of about 260 nM, whereas synaptosomes isolated in Na⁺-rich ionic media have a pH_i of 6.96±0.07 and a [Ca²⁺]_i of 463 nM, but both types of preparations have similar membrane potentials of about –50 mV when placed in choline media. The sucrose preparation takes up Ca²⁺ only by voltage sensitive calcium channels (VSCC'S) when K⁺-depolarized, while the Na⁺-rich synaptosomes take up⁴⁵Ca²⁺ both by VSCC'S and by Na⁺/Ca²⁺ exchange. The amiloride derivative 2, 4 dimethylbenzamil (DMB), at 30 M, inhibits both mechanisms of Ca²⁺ influx, but 5-(N-4-chlorobenzyl)-2, 4 dimethylbenzamil (CBZ-DMB), at 30 M, inhibits the Ca²⁺ uptake by VSCC'S, but not by Na⁺/Ca²⁺ exchange. Thus, DMB and CBZ-DMB permit distinguishing between Ca²⁺ flux through channels and through Na⁺/Ca²⁺ exchange. We point out that the different properties of the two types of synaptosomes studied account for some of the discrepancies in results reported in the literature for studies of Ca²⁺ fluxes and neurotransmitter release by different types of preparations of synaptosomes.Abbreviations used BCECF 2,7-Biscarboxyethyl-5(6)-carboxyfluorescein - BCECF/AM acetoxymethyl ester of BCECF - [Ca²⁺]_i Internal free calcium ion concentration - CBZ-DMB 5-(N-4-chlorobenzyl)-2,4-dimethylbenzamil - DMB 2, 4-dimethylbenzamil - DMSO dimethyl sulfoxide - Indo-1/AM acetoxymethyl ester of Indo-1 - MES 2-|N-Morpholino|ethanesulfonic acid - NMG N-methyl-D-glucamine - pH_i internal pH - TPP⁺ tetraphenylphosphonium - _p plasma membrane potential     

Morphological development and gibberellin production by different strains of Gibberella fujikuroi in shake flasks and bioreactor

Strain H-984 of G. fujikuroi grown for 38h in a shake flask with medium containing 20g glucose l^–1, 3g yeast extract l^–1, 2.5g NH4NO3 l^–1, 0.5g KH2PO4 l^–1, 0.1g MgSO4 l^–1, 1g CaCO₃ l^–1, and inoculated into a bioreactor with medium containing 60g glucose l^–1; 1g NH_4Cl l^–1; 3g KH2PO4 l^–1 and 1.5g MgSO₄ l^–1 produced 1100mg gibberellic acid l–1.     

The oxygen uptake-power regression in cyclists and untrained men: implications for the accumulated oxygen deficit

The regression of oxygen uptake (O₂) on power output and the O₂ demand predicted for suprapeak oxygen uptake (O_2peak) exercise (power output = 432 W) were compared in ten male cyclists [C, mean O_2peak = 67.9 (SD 4.2) ml · kg^–1 · min^–1] and nine active, yet untrained men [UT, mean O_2peak = 54.1 (SD 6.5) ml · kg^–1 · min^–1]. The O₂-power regression was determined using a continuous incremental cycle test (CON4), performed twice, which comprised several 4-min exercise periods progressing in intensity from approximately 40%–85% O_2peak. Minute ventilation (_E), heart rate (HR), respiratory exchange ratio (R), blood lactate concentration ([1a^–]_b) and rectal temperature (T _re) were measured at rest and during CON4. The slope of the O₂-power regression was greater (P 0.05) in C [12.4 (SD 0.7) ml · min^–1. W^–1] compared to UT [11.7 (SD 0.4) ml · min^–1 W^–1]; as a result, the O₂ demand (at 432 W) was also higher (P 0.05) in C [5.97 (SD 0.23) l · min^–1] than UT [5.70 (SD 0.15) 1 · min^–1]. ExerciseR and [la^–]_b were lower (P 0.05) in C .in comparison to UT at all power outputs, whereas _E and HR were relatively lower (P 0.05) in C at power outputs approximating 180 W, 220 W and 270 W. Differences in fat metabolism estimated over the first three power outputs accounted for approximately 19% of the difference in O₂-power slopes between the groups and up to 46% of the difference in O₂ at a given intensity. Although the O₂-power regressions were linear for C [r = 0.997 (SD 0.001)] and UT [r = 0.997 (SD 0.001)], the O₂-power slope was higher at power outputs at or above the lactate threshold (13.2 ml · min^–1 · W^–1 than at lower intensities (11.6 ml · min^–1 · W^–1) in C, an effect which was less profound in UT. As a result, the exclusion of O₂ at the highest power outputs completely abolished the difference in O₂-power slopes between C and UT. Thus, the relatively higher O₂ during incremental exercise in C can be almost entirely attributed to the higher O₂ cost of cycling at higher power outputs. In addition, the presence of non-linear responses in O₂ at higher intensities also confirms the invalidity of describing the O₂ response across a wide range of power outputs using a linear function, and challenges the validity of predicting the O₂ demand of more intense exercise by a linear extrapolation of this same function.     

Effects of 2-chloropropionate on venous plasma lactate concentration and anaerobic power during periods of incremental intensive exercise in humans

We investigated the effects of a stimulation of pyruvate dehydrogenase (PDH) activity induced by 2-chloropropionate (2-CP) on venous plasma lactate concentration and peak anaerobic power (W _{an, peak}) during periods (6 s) of incremental intense exercise, i.e. a force-velocity (F-) test known to induce a marked accumulation of lactate in the blood. TheF- test was performed twice by six subjects according to a double-blind randomized crossover protocol: once with placebo and once with 2-CP (43 mg · kg^–1 body mass). Blood samples were taken at ingestion of the drug, at 10, 20, and 40 Min into the pretest period, at the end of each period of intense exercise, at the end of each 5-min recovery period, and after completion of theF- test at 5, 10, 15, and 30 min. During theF- test, venous plasma lactate concentrations with both placebo and 2-CP increased significantly when measured at the end of each period of intense exercise (F = 33.5,P < 0.001), and each 5-min recovery period (F = 24.6,P < 0.001). Venous plasma lactate concentrations were significantly lower with 2-CP at the end of each recovery period (P < 0.01), especially for high braking forces, i.e. 8 kg (P < 0.05), 9 kg (P < 0.02), and maximal braking force (P < 0.05). After completion of theF- test, venous plasma lactate concentrations were also significantly lower with 2-CP (P < 0.001). The percentage of lactate decrease between 5- and 30-min recovery was significantly higher with 2-CP than with the placebo [59 (SEM 4)% vs 44.6 (SEM 5.5)%,P < 0.05]. Furthermore,W _{an, peak} was significantly higher with 2-CP than with the placebo [1016 (SEM 60) W vs 957 (SEM 55) W,P < 0.05]. In conclusion, PDH activation by 2-CP attenuated the increase in venous plasma lactate concentration during theF- test. Ingestion of 2-CP led to an increasedW _{an, peak}.     

Changes in acid-base status of marathon runners during an incremental field test Relationship to mean competitive marathon velocity

Four top-class runners who regularly performed marathon and long-distance races participated in this study. They performed a graded field test on an artificial running track within a few weeks of a competitive marathon. The test consisted of five separate bouts of running. Each period lasted 6 min with an intervening 2-min rest bout during which arterialized capillary blood samples were taken. Blood was analysed for pH, partial pressure of oxygen and carbon dioxide (P0₂ and PCO₂) and lactate concentration ([la^–]_b). The values of base excess (BE) and bicarbonate concentration ([HCO₃ ^–]) were calculated. The exercise intensity during the test was regulated by the runners themselves. The subjects were asked to perform the first bout of running at a constant heart rate f _c which was 50 beats · min^–1 below their own maximal f _c. Every subsequent bout, each of which lasted 6 min, was performed with an increment of 10 beats · min^–1 as the target f _c. Thus the last, the fifth run, was planned to be performed with fc amounting to 10 beats · min^–1 less than their maximal f _c. The results from these runners showed that the blood pH changed very little in the bouts performed at a running speed below 100% of mean marathon velocity ( _m). However, once _mwas exceeded, there were marked changes in acid-base status. In the bouts performed at a velocity above the _mthere was a marked increase in [la^–]_b and a significant decrease in pH, [HCO₃ ^–], BE and PCO₂. The average marathon velocity ( _m) was 18.46 (SD 0.32) km·h^–1. The [la^–]_b at a mean running velocity of 97.1 (SD 0.8) % of _mwas 2.33 (SD 1.33) mmol ·l^–1 which, compared with a value at rest of 1.50 (SD 0.60) mmol·l^–1, was not significantly higher. However, when running velocity exceeded the vm by only 3.6 (SD 1.9) %, the [la^–]b increased to 6.94 (SD 2.48) mmol·l-1 (P<0.05 vs rest). We concluded from our study that the highest running velocity at which the blood pH still remained constant in relation to the value at rest and the speed of the run at which [la^–]_b began to increase significantly above the value at rest is a sensitive indicator of capacity for marathon running.     

Three-dimensional organization of smooth muscle cells in blood vessels of laboratory rodents

Summary Three-dimensional aspects of smooth muscle cells of the microvas-culature were studied ultrastructurally in laboratory rodents by means of serial thin sections and reconstruction of muscle cell models. It was demonstrated that a muscle cell of an arteriole (luminal diameter (LD) 17 m) in hamster striated muscle was spindle-shaped, 70 m long, and wound twice round the vessel axis. The volume of the cell was calculated as 750 m³ and its surface area as 1330 m². A muscle cell in an arteriole (LD 6 m) in the rat retina was irregular in shape, about 22 m long, and had branched processes. The cell volume was calculated as 139 m³ and its surface area as 298 m².     

INFLUENCE OF A LOW-DOSE COX-2 INHIBITOR DRUG ON EXERCISE-INDUCED INFLAMMATION,MUSCLE DAMAGE AND LIPID PEROXIDATION

The purpose of this study was to examine the effect of acute low-dose celecoxib administration on exercise-induced inflammation, muscle damage and lipid peroxidation. Twenty healthy untrained males (age: 25.5±4.5 yrs, weight: 72.7±7.9 kg, height: 177.3±7.2 cm) were randomly assigned to treatment (T) or placebo (P) groups. Blood samples were obtained before, immediately after, 3 h after and 24 h after exercise. Subjects ran for 30 min at 75% V.O₂ max on a treadmill. Participants consumed 100 mg celecoxib or a placebo immediately after and 12 h after the immediately post-exercise blood sample. Total leukocytes, neutrophils, creatine kinase (CK), C-reactive protein (CRP) and malondialdehyde (MDA) were assessed at each time point. Significant increases in total leukocytes and neutrophils were observed 3 h after exercise in both groups (P < 0.05). CK and CRP levels were significantly increased immediately, 3 h and 24 h after exercise in both groups (P < 0.05). A significant increase in MDA was observed immediately after exercise in both groups (P < 0.05); however, no significant group differences were observed for MDA or CK. These findings suggest that inhibition of cyclo-oxygenase activity with low-dose celecoxib does not affect exercise-induced inflammation, muscle damage, or lipid peroxidation.     

Signal transduction pathways of muscarinic receptors in circular smooth muscle from the rabbit caecum

The effects of muscarinic acetylcholine receptor stimulation on phosphoinositides breakdown and adenylate cyclase activity were examined in the circular smooth muscle of the rabbit caecum. InMyo-[³H]inositol-labeled circular smooth muscle cells, carbachol caused a concentration-dependent increase in [³H]inositol phosphates ([³H]IPs) accumulation (EC₅₀ of 3±1 M). The M₁-selective antagonist pirenzepine (PRZ), the M₂-selective AF-DX 116 (11-2[[2-[(diethyl-amino)methyl]-1-piperidinyl]acetyl]-5, 11-dihydro-6Hpyrido[2,3-b][1,4]benzodiazepin-6-one) and the M₃-selective para-fluoro-hexahydrosiladifenidol (p-F-HHSiD) inhibited the carbachol-induced [³]inositol phosphates accumulation with the following order of potency: p-F-HHSiD>PRZ>AF-DX 116. In saponin-permeabilized circular smooth muscle cells, carbachol and GTP[S] elicited a concentration-dependent increase in [³H]inositol phosphates accumulation. The concentration-response curve for GTP[S] was shifted to the left when cells were incubated with 1 M carbachol. The [³H]inositol phosphates accumulation elicited by simultaneous addition of 0.1 M GTP[S] and 1 M carbachol to permeabilized cells was significantly decreased (78.28±18.23% inhibition) when cells were preincubated for 5 min with 0.1 mM GDP[S]. In nonpermeabilized cells, pertussis toxin did not alter the carbachol-induced increase in [³H]inositol phosphates accumulation. On the other hand, the 0.1 mM carbachol-induced inhibition of forskolin-stimulated adenylate cyclase activity in circular smooth muscle homogenates was significantly reversed by atropine and AF-DX 116, whereas PRZ and p-F-HHSiD were ineffective (muscarinic antagonists were used at 1 M final concentration). Moreover, the carbachol-induced inhibition of the cyclic AMP accumulation elicited by 10 M isoproterenol was abolished by pertussis toxin pretreatment of isolated circular smooth muscle cells. In conclusion, our data suggest that in circular smooth muscle of rabbit caecum, the muscarinic receptor stimulation of [³H]inositol phsophates accumulation is mediated by M₃ subtype receptors coupled to a pertussis toxin-insensitive G protein, whereas inhibition of adenylate cyclase activity is mediated by M₂ subtype receptors coupled to a pertussis toxin-sensitive GTP-binding protein G_i.     

An equatorial tri-iron substituted Wells-Dawson type tungstophosphate with magnetic and bifunctional electrocatalytic properties

Interaction of the hexa-lacunary polyanion precursor [α-H₂P₂W₁₂O₄₈]¹²⁻ and the Fe^III in aqueous solution results in the formation of an equatorial tri-iron substituted Wells-Dawson type compound, K₄Cs₂Fe₂[P₂W₁₅(FeOH)₃O₅₉]·22H₂O (1). Compound 1 was characterized by IR, elemental, single-crystal X-ray diffraction, thermogravimetric, magnetic, as well as electrochemical analysis. The polyoxoanion [P₂W₁₅(FeOH)₃O₅₉]¹²⁻ can be viewed as a derivative of the parent polyoxoanion [α-P₂W₁₈O₆₂]⁶⁻ by removal of three belt WO groups and then inhabited by three FeOH groups. The compound 1-modified carbon paste electrode (1-CPE) presents good electrocatalytic activity not only toward the reduction of nitrite which is attributed to the function of tungstophosphate, but also toward the oxidation of ascorbic acid which is primarily attributed to the function of Fe^III. The magnetic properties of 1 have been studied by magnetic susceptibility and fitted according to an isotropic exchange model. Compound 1 exhibits strong antiferromagnetic spin exchange interactions between the Fe^III centers.     

Activation of two types of fibres in ferret,Mustela putorius furo,cremaster muscle

Summary Some contractile, histochemical, morphological and electrophysiological properties of ferret, Mustela putorius furo, cremaster muscle have been estimated. Histochemical fibre typing revealed the presence of two types of fibres (type I 66.2%, type II 33.8%). Morphometry performed on ATPase-stained transverse sections showed that type I was composed of a large amount (40%) of small(<400 m²) cells. In mammalian Ringer two groups of fibres could be recognized on the basis of the values of resting potential (-69.7 mV and-59.1 mV) and intracellular sodium activity (8.3 mmol·l^-1 and 14.1 mmol·l^-1, respectively). In experiments on fibre bundles, the elevation of extracellular potassium concentration to 15–200 mmol·l^-1 produced contractures that consisted of a well-defined transient or phasic tension followed by a sustained or tonic tension. Properties of activation and inactivation of the tension analysed in small bundles of cut fibres (lengths 0.5–1.0 cm) were of fast- and slow-twitch type for phasic and tonic phase, respectively. In contrast to the phasic component of K contractures, the tonic phase was abolished by Ca²⁺ withdrawal and inhibited by Ni²⁺, Cd²⁺, Co²⁺, Gd³⁺ and gallopamil (D600). In Ca²⁺-free medium the sustained tension was restored by adding Sr²⁺. It is concluded that in ferret cremaster muscle the presence of slow-twitch fibres would give rise to the tonic component of the K contracture in which an extracellular source of activator Ca²⁺ is involved. The ability of these fibres to contract with a maintained tension for prolonged periods of time might participate in the temperature regulation of the testes.Abbreviations a _i ^Na intracellular sodium activity - ATPase myosin adenosine triphosphatase - D600 gallopamil - E _m membrane potential - E _r resting potential - EDL muscle, extensor digitorum longus muscle - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulphonic acid - e.c. excitation-contraction - SDHase succinate dehydrogenase - NADHase nicotinamide adenine, dinucleotide hydrogen-diaphorase - SOL muscle, soleus muscle - T time constant of relaxation - TEACI tetraethylammonium chloride - [Ca]_o, [K]_o, [Na]_o extracellular calcium, potassium, sodium concentration     

Reduced superhelicity of plasmid DNA produced by the rho-15 mutation in Escherichia coli

Summary The plasmid pJSF6, a derivative of pBR327, could be maintained at 30° C in strains of Escherichia coli containing the strong rho mutation, rho-15. Plasmids extracted from rho-15 cells were always less negatively supercoiled than plasmids from rho ⁺ cells. Transduction experiments designed to separate the rho gene from possible extragenic suppressors showed that the rho allele consistently determined the degree of plasmid superhelicity. Comparison of the superhelicity of plasmids extracted from the rho-15 and from a gyrB mutant showed that at 30° C the negative supercoiling was reduced by the amounts W _rho=4.0±0.3 and W _gyr=6.0±0.3 turns; the effect of the rho-15 mutation on supercoiling was thus comparable to that of the gyrB mutation. A similar effect of the rho-15 mutation on the superhelicity of pBR329 was observed. The observation that the Rho protein has a role in determining DNA superhelicity (though not necessarily a direct role) provides a new point of view for studying the pleiotropic properties of rho mutants.We dedicate this paper to the cherished memory of Ethel S. Tessman, who died May 10, 1986. She encouraged and advised and stimulated each of us in the development of our careers     

DIFFERENT RECOVERY METHODS AND MUSCLE PERFORMANCE AFTER EXHAUSTING EXERCISE: COMPARISON OF THE EFFECTS OF ELECTRICAL MUSCLE STIMULATION AND MASSAGE

In this study we assessed the influence of the three different recovery interventions massage (MSG), electrical muscle stimulation (EMS), and passive rest (PR) on lactate disappearance and muscle recovery after exhausting exercise bouts. Twelve healthy male sport students participated in the study. They attended the laboratory on five test days. After measurement of V.O₂max and a baseline Wingate test (WG_b), the three recovery interventions were tested in random counterbalanced order. High intensity exercise, which consisted of six exhausting exercise bouts (interspersed with active recovery), was followed by MSG, EMS or PR application (24 minutes); then the final Wingate test (WG_f) was performed. Lactate, heart rate, peak and mean power, rating of perceived exertion (RPE), and total quality of recovery (TQR) were recorded. In WG_f mean power was significantly higher than in WG_b for all three recovery modalities (MSG 6.29%, EMS 5.33%, PR 4.84% increase, p < 0.05), but no significant differences in mean and peak power were observed between the three recovery modes (p > 0.05). The heart rate response and the changes in blood lactate concentration were identical in all three interventions during the entire protocol (p = 0.817, p = 0.493, respectively). RPE and TQR scores were also not different among the three interventions (p > 0.05). These results provide further evidence that MSG and EMS are not more effective than PR in the process of recovery from high intensity exercise.     

Intramolecular exchange of coordinated and dangling phosphines in pentacarbonyl group 6 complexes of 1,1,2-tris(diphenylphosphino)ethane

The linkage isomers, (OC)₅M[κ¹-PPh₂ CH₂CH(PPh₂)₂] 1 and (OC)₅M[κ¹-PPh₂ CH(PPh₂)CH₂PPh₂] 2 (M = Cr, Mo and W) exist in equilibrium at room temperature. Equilibrium constants for 1Cr ? 2Cr, 1Mo ? 2Mo and 1W ? 2W at 25 °C in CDCl₃ are 2.61, 5.0 and 4.74, respectively. Enthalpy favors the forward reaction (ΔH = −13.5, −12 and −12.2 kJ mol⁻¹, respectively) while entropy favors the reverse reaction (ΔS = −37.6, −28 and −28.2 J K⁻¹ mol⁻¹, respectively). Isomerization is much faster than chelation with 1Mo ? 2Mo ? 1W ? 2W > 1Cr ? 2Cr. Enthalpies of activation for 1Cr ? 2Cr and 1W ? 2W are 119.0 and 92.6 kJ mol⁻¹, respectively, and entropies of activation are 1.4 and −28.2 J K⁻¹ mol⁻¹, respectively. Isomerization is 10⁴ times faster for these complexes than for (OC)₅M[κ¹-PPh₂CH₂CH₂P(p-tolyl)₂]. A novel mechanism is proposed to account for the rate differences. The X-ray crystal structure of 2W shows that the phosphorus atom of the short phosphine arm lies very close to a carbon atom of the W(CO)₄ equatorial plane (3.40 Å) which could allow “through-space” coupling, accounting in part for the observation of long-range J_PC and J_PW coupling. The X-ray structure of (OC)₅W[κ¹-PPh₂ C(CH₂)PPh₂] 5W has been determined for comparison to 2W.     

Skeletal muscle pH dynamics during arousal from hibernation measured by31P NMR spectroscopy

Summary The time-course of changes in skeletal muscle pH during arousal from hibernation in the Columbian ground squirrel was studied using³¹P NMR spectroscopy. In hibernation (T _re 7–9°C), shoulder/neck muscle pH was 7.45±0.03 and _Im was 0.60. In euthermia (T _re 37°C), muscle pH was 7.24±0.05 and _Im was 0.75. Thus the overall pH-temperature coefficient was-0.009 pH units/°C, indicating acidification of the muscle in hibernation. During the transition from hibernation to euthermia, however, the muscle shows a nonlinear pattern of pH change. In early arousal (T _sh<20–25°C,T _re<15°C) muscle pH does not change and muscle _Im increases to 0.72. In later arousal (T _sh>20–25°C,T _re>15°C) muscle pH decreases gradually toward the euthermic value and muscle _Im increases only slightly from 0.72 to 0.75. These results support the hypothesis that intracellular acidification of the muscle, present during hibernation, is reversed in early arousal. This may facilitate an increase in muscle metabolism and the contribution of maximal shivering thermogenesis to rewarming of the animal.Abbreviations _Im dissociation ratio of protein imidazole buffergroups - NST non-shivering thermogenesis - BAT brown adipose tissue - dp H/dT temperature coefficient of pH - pH _i intracellular pH - ³¹ P NMR ³¹Phosphorus nuclear magnetic resonance - P _i chemical shift of inorganic phosphate relative to PCr - PCr phosphocreatine - T _b body temperature - T _re rectal temperature - T _sh subcutaneous shoulder temperature - T _a ambient temperature